Known integrated gasification combined cycle (“IGCC”) power generation systems may include a gasification system that is integrated with at least one power producing turbine system. For example, known gasifiers may convert a mixture of a fuel such as coal with air or oxygen, steam, and other additives into an output of a partially combusted gas, typically referred to as a “syngas”. These hot combustion gases may be supplied to a combustor of a gas turbine engine. The gas turbine engine, in turn, powers a generator for the production of electrical power or to drive another type of load. Exhaust from the gas turbine engine may be supplied to a heat recovery steam generator so as to generate steam for a steam turbine. The power generated by the steam turbine also may drive an electrical generator or another type of load. Similar types of power generation systems also may be known.
The known gasification processes also may generate flows of nitrogen. For example, an air separation unit may be used to generate a supply of oxygen to the gasifier. The air separation unit may generate oxygen by separating the oxygen from the nitrogen in a supply of air. Some of the nitrogen may be used to control emissions generated by the gas turbine engine or to augment power output of the turbine. For example, nitrogen may be injected into the combustion zone of the gas turbine engine to reduce the combustion temperatures and to reduce nitrous oxide (“NOx”) emissions. The turbine section of the gas turbine engine is cooled to maintain component temperatures to allowable material limits. The cooling, which is provided by air extracted from the compressor section, penalizes engine power output and heat rate.
There is thus a desire for an improved integrated gasification combine cycle power generation system. Such an IGCC system preferably would use all or most of the nitrogen generated therein for productive purposes while improving overall IGCC output and heat rate.